Cathode support structure



Nov. 2, 1965 R. P. WATSON ETAL 3,215,884

CATHODE SUPPORT Filed April 27, 1961 INVENTORS:

ROBERT P. WATSON JOHN L. WILSON,

THEIR ATTORNE United States Patent() 3,215,884 CATH-IODE SUPPORT STRUCTURE Robert P. Watson, Schenectady, and lohn L. Wilson, Guilderland Center, NY., assignors to General Electric Company, a corporation of New York Filed Apr. 27, 1961, Ser. No. 106,097 7 Claims. (Cl. 313-178) This invention relates to electron discharge devices and more particularly to improvements in the mounting of electrodes in parallel plane electron discharge devices.

In the manufacture of high frequency electron discharge devices including planar electrode elements, accurate close spacing and parallelism of the electrode elements are extremely critical considerations, and it is desirable to provide prefabricated electrode subassembly structures, such as cathode and anode subassemblies, which when employed in completing an assembled electron discharge device will insure such accurate close spacing and parallelism of the electrode elements. Also, in view of the fact that high frequency electron discharge devices are often structurally very small and include component parts which, due to their small sizes, are extremely difficult to manipulate and assemble, it is desirable to provide electrode subassembly structures which can be readily manufactured, checked for accuracy before assembly in an overall device, and which are constructed to facilitate manufacture in general and reduce shrinkage, or the number of rejected completely assembled tubes. Additionally, in such devices it is generally desirable that a symmetrical uniform radio frequency path be provided from an annular external contact surface to a planar cathode surface. Still further, it is desirable in many high frequency electron discharge devices to employ a parasitic getter structure, or one which relies upon cathode lament heat to render a quantity of getter material effective in sorbing undesired gases. When such is the case, it is desirable to provide structure which can be constructed without substantial manufacturing difliculties resulting, for example, from the small size of the elements involved. It is also desirable that the structure be adapted for assuring optimum effective heating of the getter material and for avoiding undesired reaction between different materials of the structure.

Accordingly, a primary object of the present invention is to provide a new and improved arrangement for mounting the active cathode surface in parallel plane electron `discharge devices and for providing a uniform symmetrical radio frequency path thereto from an external annular electrical contact surface.

Another object of the present invention is to provide new and improved means for mounting planar active surface anode elements in electron discharge devices.

Another object of the present invention is to provide new and improved means adapted for assuring closelyspaced parallel positions of planar electrodes in electron discharge devices.

Another object of the present invention is to provide new and improved means for mounting a getter structure in an electron discharge device.

Still another object of the present invention is to provide new and improved means for facilitating the manufacture and assembly of parallel plane electron discharge ICC devices and minimizing manufacturing shrinkage therein.

Further objects and advantages of this invention will become apparent as the following description proceeds and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

In carrying out the objects of the invention there is provided an electron discharge device including an envelope comprising a stacked array of ceramic and metal annular members. One of the metal members comprises a cathode contact and has an end soldered to a transverse end surface of one of the ceramic members. A cathode structure comprising a planar emitter is mounted on the end of a conductive support sleeve and extends through the central opening in the mentioned one ceramic member. Coaxially located in respect to the one ceramic member and bonded to the mentioned transverse end surface thereof is a washer-like metal member which is interposed between the end of the cathode contact and transverse end of the one ceramic member. The washerlike element includes a plurality of circumferentially spaced centripetally extending tabs spot-Welded to the cathode support sleeve and supports the latter element in the ceramic member in coaxial spaced relation thereto. The washer-like element further includes an outer rim fitted over the end of the cathode Contact member and thereby maintained in coaxial relation thereto. The cathode assembly further includes a dependent tubular extension coaxially located in the support sleeve, corresponding in length generally to the sleeve and having a ared outer end. Fitted over the extension and joined thereto only at the rim of the flare is a getter support sleeve which extends the full length of the extension. The latter sleeve bears a quantity of getter material and is formed of a material which is non-alloying with the getter material and the material of the extension. The arrangement including the cathode structure, the washerlike element and the ceramic member on which the washer-like element is mounted comprises a subassembly which is preferably prefabricated. The device includes a prefabricated anode subassembly comprising a generally washer-like ceramic envelope wall section having an inwardly extending inner rim portion with a planar transverse end surface. An anode element including a shank and an enlarged head portion is provided and can be positioned with the shank tightly fitted in the aperture in the ceramic section. The back of the head portion of the anode element comprises a planar transverse surface and is butt-sealed to the planar transverse end surface on the inner rim of the ceramic section.

For a better understanding of the invention, reference may be had to the accompanying drawing wherein:

FIGURE l is a sectional view of an electron discharge device embodying the various features of my invention; and

FIGURE 2 is an enlarged fragmentary perspective view of a portion of the cathode subassembly included in the device of FIGURE l.

Referring to the drawing, the electron discharge device there illustrated includes three annular metal members 1, 2 and 3 which are arranged in spaced relation and separated from one another by annular ceramic insulative members 4 and 5 sealed therebetween. Both the metal members 1, 2 and 3 and the insulators i and 5 are of progressively decreasing diameters from one end to the other of the device so that the device has a stepped configuration. Additionally, the metal members constitute combined wall sections and electrical contact surfaces of the device and the ceramic members constitute insulative wall sections of the device.

The upper end of the device comprises an anode subassembly including a generally washer-like ceramic wall section 6. Mounted coaxially in the wall section 6 is an anode element generally `designated 7 and which includes a tubular shank 8 and an enlarged head portion 9. The shank 8 is dimensioned for fitting in the ceramic member 6 and the tit can be tight for affording supporting contact of the ceramic member with the outer surface of the shank for a substantial axial length thereof directly behind the head portion 9. The head 9 includes a transverse back surface 10. The back surface 1t) engages and makes substantial area contact with a planar transverse end surface 11 formed on an inwardly extending inner rim portion 12 on the ceramic member 6. Additionally, a suitable ceramic-to-metal bond is provided between the surfaces and 11 of the head 9 and rim 12, respectively, thereby to provide a butt seal between these areas. This arrangement enables prefabrication of a Subassembly including the anode 7 and ceramic wall section 6 and checking of same for strength and accurate positioning of the anode element before incorporation in an overall device. Additionally, if provided, the substantial area contact between the outer surface of the shank 8 and the inner surface of the aperture in the member 6 serves to protect the butt seal between the anode head and ceramic member by relieving any strain thereon as caused by laterally directed forces applied on the shank 8 when, for example, electrical connections are made thereto.

The anode element 7 includes the usual planar active surface designated 13. Additionally, it includes transversely extending passageways 14 communicating with the axial passage through the shank 8. These passages enable exhaust of the device and, in practice, upon completion of the envelope of the device and after the exthe ceramic section 5. The grid washer 15 is spaced from the ceramic section 6 by an acurately dimensioned spacer 15a which determines the interelectrode spacing between the grid Wires 16 and the active anode surface 13. The outer rim portions of the ceramics 5 and 6, the grid washer 15 .and the spacer 15a are joined by a suitable hermetic and conductive bond to the inner surface of the metal member 3 which is thereby adapted for serving as a grid contact.

The ceramic section 5 includes a central aperture 18 which can be of any desired configuration. The member 5 comprises a portion of a cathode subassembly. More specifically, the member S includes a planar transverse end surface 19 at the lower end thereof and to which is suitably bonded, as by means of a suitable ceramic-tometal bond, a washer-like metal member 20. The metal member 20 includes an outer dependent rim 21 which fits over an end portion of the above-mentioned metal member 2. The metal member 2, in turn, is bonded to the ceramic member 5 by a suitable ceramic-to-metal bond indicated at 22. This arrangement provides for coaxial relative location of the washer-like member 20 and the metal contact member 2 as well as a desirable uniform circumferential electrical contact therewith.

Formed off the inner rim of the washer-like member 20 are a plurality of circumferentially spaced centripetally extending tabs 23. As perhaps better seen in FIGURE 2, the tabs 23 are preferably three or more in number, are

equally spaced and extend both inwardly and longitudinally. The tabs 23 are spot-welded to the outer surface of a metal foil cathode support sleeve 24. To the upper end of the cathode support sleeve is suitably secured a planar emitter 25 which is adapted for extending parallel and in closely spaced relation to the grid wires 16 and anode active surface 13. Additionally, the tabs 23 extend suticiently inwardly such that the sleeve 24 is maintained in coaxial spaced relation to the inner surface of the aperture 13 and the inner rim of the member 2t). This structure provides for rigid mounting of the cathode structure and for Va uniform symmetrical radio frequency path between the contact member 2 and the emitter. It also provides for thermal isolation of the cathode structure since the tabs constitute relatively small thermal paths. This enhances cathode efficiency and minimizes heater power requirements. Further, this structure enables prefabrication of a cathode subassembly structure including the ceramic member 5, the washer-like element 20 and the cathode structure including the support sleeve 24 and all of the other cathode elements supported thereby. This, in turn, facilitates overall assembly of the tube, enables checking for parallelism between the active surface of the emitter and the grid reference surface on which the element 17 rests and assures a satisfactory electrical contact between the cathode structure and contact 2 when the latter is sealed to the ceramic member 5 in the manner shown.

Where, for example, heat transfer from the cathode structure is not a major concern the washer-like member 2t) need not include inwardly extending tabs 23 but, instead, could have the cathode support sleeve 24 directly secured to the inner rim of the member 20.

Mounted on the emitter 25 and extending coaxially in relation to the support sleeve 24 is a dependent tubular extension 26 having a flange 26a spot welded to the underside of the emitter. The extension 26 extends for the full length of the support sleeve 24 and houses a lamentary heater 27 adapted when energized to render the emitter 25 emissive. The lower end of the extension 26 is flared as at 28. Fitted over the extension 26 is a foil metal getter support sleeve 29 which abutts at the upper end thereof against the iiange 26a of the extension and is welded at the lower end to the rim of the Hare 28. This arrangement provides for longitudinal predetermined spacing between the extension 26 and the sleeve 29. Additionally, it enables assembly of the sleeve 29 easily and simply by inserting the sleeve over the extension and welding the lower end of the sleeve 29 to the flared rim of the extension 26.

In actual construction the overall length of the disclosed tube is only about 1 inch and the just-described cathode assembly is extremely small, therefore, the described arrangement for mounting the sleeve 29 facilitates greatly the manufacture of the lcathode assembly because it allows assembly merely by sliding one element over the other .and enabling welding at an accessible region and does not require welding or any other securing effort -internally of the support sleeve 24. Additionally, and as indicated above, the support sleeve 29 carr1es a quantity of getter material, which, as illustrated, can be in t-he form of a foil sleeve suitably mounted on the sleeve 29. The getter sleeve is mounted on the sleeve 29 before the latter is inserted over and secured to the extension 26 and can be formed Vof any suitable getter material. Still further, the sleeve 29 is formed of a metal which is non-alloying with the metal of either the getter material or the extension 26. Preferably, the sleeve 29 is formed of tantalium while the extension 26 is formed of nickel and the getter material 30 comprises a sleeve of titanium or zirconium, or an alloy of both which can advantageously have the com-position of the alloy disclosed -in US. Patent No. 2,926,981, Stout et al. issued March 1, 1960, and assigned to the same assignee as the present invention.

The heater 27 can consist of a double helix of tungsten or any of the well-known metals or lalloys suitable for use as heating filaments in electron ldischarge devices. The end of one of the leads 31 of the heater is suitably interpositioned between the previously mentioned contact member 1 and a tubular ceramic section 32 sealed in the member 1. Thus, electrical connection between the contact member 1 and one side of the heater is effected. The other filament lead 33 is interpositioned between the ceramic section 32 and a terminal rod 34, sealed centrally in the insulator 32. Thus, the coaxially arranged contacts 1 and 34 serve for completing lan energizing circu-it through the heater 27.

In fabricating the illustrated device, the cathode assembly is prefabricated as a subassembly and with the aid of suit-able fixtures to provide coplanarity of the upper planar surface of the insulator 5 and the planar active surface of the emitter 25. Additionally, the anode assembly, including the ceramic section 6 with the anode element bonded thereto, is .prefabr-icated in the abovedescribed manner. Thereafter, the cathode and anode subassemblies and the various other described `parts are stacked in the manner illustrated and are held in position with the aid of a brazing xture. The various seals between the ceramic and metal elements other than those employed in prefabricating the cathode and anode subassemblies are formed as by interpositioning rings of solder material in the regions where the seals are to be effected and heating the overall assembly to the melting point of the solder material in order to enable it to iioW between the elements to be joined. Subsequent to the Iforming of these seals the device is evacuated through the above-discussed passages in the anode 7 and these passages are :sealed as by provision of a suitable quantity of solder material 36 in the upper end of the shank 8.

While a specific embodiment of the present invention has been described and illustrated, it is not desired that the invention be limited to the particular forms shown and described, and it is intended by the appended claims to cover all modifi-cations within the spirit and scope of our invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. An electrode assembly comprising an insulative annular member, a coaxial tubular metal contact member having the rim thereof brazed to a transverse end surface of said annular member, a coaxial washer-like metal element bonded to said transverse end surface of said annular member and interposed between said transverse end surface and said rim of said Contact member for making an electrical connection to the latter, a dependent outer rim on said washer-like element extending over the rim of said contact member for coaxially relating said washer-like element and said contact member, a

cathode assembly extending into said annular member and including a metal cathode support sleeve, and a plurali-ty of centripetally and longitudinally extending tabs forme-d off the inner sleeve for supporting said cathode assembly and providing a uniform symmetrical electrical connection between said cathode assembly and contact member.

2. An electrode assembly comprising an insulative annular mem-ber having `a central aperture, a -metallic washer-like element having a plurality 0f circumferentially spaced, centripetally extending tabs formed off its inner rim, said element being secured coaxially to a transverse end surface of said annular member, and a cathode assembly extending into said annular member and including a metal cathode support sleeve extending through said central aperture in coaxial spaced relation to the wall of said aperture, said Isleeve being bonded to the centripetally extending tabs of said washer-like element in a low thermal 4conductivity joint.

3. An electrode assembly compri-sing an insulative annular member having a central aperture, a coaxial tubu- 6 lar metal contact member having the rim thereof brazed to a transvense end surface of said annular member, a coaxial washer-like metal element having a plurality of circumferentially spaced, -centripetally extending tabs `formed olf its inner rim, said element being securely positioned between said rim .of said contact member and said transverse end surface of said annular member and electrically contacting said contact member, a cathode assembly extending into said annular member and including a metal cathode support sleeve extending through said central aperture in coaxial spaced relation to the wall of said aperture and said cathode support sleeve being bonded to the centripetally extending tabs of said washer-like element.

`4. An electrode assembly according to claim 3, wherein said washer-like element includes an outer dependent rim portion extending over said rim of said contact member for maintaining said washer-like elementand cath-ode assembly in coaxial relation to said contact member.

5. An electrode assembly comprising an insulative annular member, a metallic washer-like element secured -coaxially to a transverse end surface of said annular member, and a cathode assembly extending into said annular member and including a metal cathode support sleeve extending through and bonded to the inner rim portion of said Washer-like element, a metal disc-like emitter, a coaxial tubular extension on one side of said emitter, a heater located in said extension, said cathode ysupport sleeve having an end secured to the periphery of said emitter and extending in coaxial spaced relation about said extension, a getter support sleeve fitted over said extension and secured thereto at the outer end thereof, a quantity of getter material carried by said getter 1support sleeve, and said getter support sleeve comprising a material which is non-alloying with the material of sai-d extension and getter at normal operating temperatures of said device.

6. An electrode assembly comprising an insulative annular member, a metallic washer-like element secured coaxially to -a transverse end surface of said annular member, and a cathode assembly extending into said annular member and including a metal cathode support sleeve extending through and bonded td the inner rim portion of said washer-like element, a metal disc-like emitter, a coaxial `tubular extension on one side of said emitter and including a flared outer end, a heater located in -said extension, said cathode support sleeve having an end secured to the periphery of said emitter and extending to coaxial spa-ced relation about said extension, a getter support sleeve fitted over said extension and secured at the outer end thereof to the fiared end of said extension, .a quantity lof getter material carried by said getter support sleeve, and said getter support sleeve comprising a material which is non-alloying with the material of said extension and said getter material at normal operating temperatures of said device.

7. An electrode assembly comprising an insulative annular member, a metallic washer-like element secured coaxiaily to a transverse end surface of said annular member, and a cathode assembly extending int-o said annular member and including a metal cathode support sleeve extending through and bonded to the inner rim portion of said washer-like element, a metal disc-like emitter, a coaxial tubular extension on one side of said emitter 4including a flared outer end, a heater locate-d in said extension, said cathode support sleeve having an end -secured in coaxial spaced relation to said extension and corresponding generally in length to said extension, a getter support sleeve fitted over and extending the full length of said extension, said getter support sleeve being joined at the outer end thereof to `the fiared end `of said extension and thereby mounted in coaxial spaced relation to the major portion of said extension, a quantity of getter material carried by said getter support sleeve, said getter support sleeve comprising a material which is non-alloying with the material of said extension and said getter material at normal operating temperatures .of `said device.

References Cited by the Examiner UNITED STATES PATENTS 8 Yoder 313-174 Watson et al 313-270 X Wadia et al. 313-174 Doolittle 313-174 X Rose et al 313-284 Kahl 313-270 GEORGE N. WESTBY, Primary Examiner.

RALPH G. NILSON, ROBERT SEGAL, Examiners. 

2. AN ELECTRODE ASSEMBLY COMPRISING AN INSULATIVE ANNULAR MEMBER HAVING A CENTRAL APERTURE, A METALLIC WASHER-LIKE ELEMENT HAVING A PLURALITYOF CIRCUMFERENTIALLY SPACED, CENTRIPETALLY EXTENDING TABS FORMED OFF ITS INNER RIM, SAID ELEMENT BEING SECURED COAXIALLY TO A TRANSVERSE END SURFACE OF SAID ANNULAR MEMBER, AND A CATHODE ASSEMBLY EXTENDING INTO SAID ANNULAR MEMBER AND INCLUDING A METAL CATHODE SUPPORT SLEEVE EXTENDING THROUGH SAID CENTRAL APERTURE IN COAXIAL SPACED RELATION TO THE WALL OF SAID APERTURE, SAID SLEEVE BEING BONDED TO THE CENTRIPETALLY EXTENDING TABS OF SAID WASHER-LIKE ELEMENT IN A LOW THERMAL CONDUCTIVITY JOINT. 